The invention relates to a cartridge set for dispensing in-situ foam, with polyol being contained in one cartridge and isocyanate being contained in another cartridge, and with both cartridges opening into a common, elongated mixing nozzle, via which foam produced from the said substances as components is dispensed.
Sets designed as twin cartridges are commercially available, as are suitable gun-like dispensing devices. A more syringe-like double cartridge is disclosed by U.S. Pat. No. 4,538,920.
As far as use of the foam is concerned, there is a wide range, from the fitting of door and window frames to the filling of joints.
On the other hand, there are also types of foam strip with a heat-expandable intumescent compound, for example a urea-derivative/ammonium-polyphosphate/polyacetate-based compound. In this respect, reference is made to DE-U 93 10 222.
DE-A 36 12 377 discloses a flameproof sealing strip, likewise with a thermally reactive intumescent additive. The strip is used in the building trade.
Recently, attention has also been paid to the use of expandable graphite as a flame-retardant additive. In the event of a fire, this mineral rapidly assumes up to 280 times its initial volume and smothers the fire.
The expansion of the graphite begins at approximately 200xc2x0 C. and it attains its greatest space-taking effect at 900xc2x0 C.
With knowledge of these given facts, it is an object of the invention to make the said expanding substance available to the building foam sector in a way which is advantageous in terms of dispensing.
This object is achieved initially and substantially in the case of a cartridge set according to the above-mentioned type wherein portions of expandable graphite are contained at least in one of the cartridges. The expanding substance held in readiness in this way makes use of already existing receptacles. Added to this is the use of the mixing nozzle, likewise already provided on the cartridge set. An extremely fine distribution takes place in this nozzle. According to the invention, it is then proposed that the portions of expandable graphite are accommodated in the cartridge containing polyol as an embedding substance. On the other hand, it can also be advantageously provided that the portions of expandable graphite are accommodated in the cartridge containing isocyanate as an embedding substance. Furthermore, it is favourable if the portions of expandable graphite are added to the substances such that they are distributed between the two cartridges. This solution is further characterized by a uniform distribution between the substances of the two cartridges. Ifxe2x80x94as also proposedxe2x80x94both cartridges have portions of expandable graphite, there is already from the outset as it were a balanced convergence of the portions. The expansion property also much depends on the size of the graphite portions. As has been found, it is suitable for the graphite portions to have a longest extent of approximately 0.1 mm to 0.3 mm. An extent in this respect of 0.15 mm is preferred. Even sometimes coarser flake graphite can still be dispensed by means of the cartridge set, since the outlet nozzle cross-section of the mixing nozzle has a diameter of 2 mm to 5 mm. With this order of magnitude, a satisfactory passage of the mixed substances to be dispensed, of in-situ foam enriched with graphite portions and comprising two components, namely a polyol mixture and modified isocyanate, is obtained. The incorporation of the graphite portions is mechanically assisted further by the length of the mixing nozzle in the region of the mixing zone corresponding to ten to twenty times the diameter of the mixing nozzle tube. The diameter is a good 9 mm, this meaning the clear diameter. With regard to the good distribution of the expanding substance referred to, it is regarded as advantageous for approximately 40 graphite portions to occur on 1 cm2 of surface of the (solidified) foam or like cross-sectional area. As has been found, there is a high degree of effectiveness if the proportion of the graphite in relation to the embedding substance is 10-20%.